1. Field of the Invention
This invention relates generally to the contraction of soft tissue, and more particularly, to the compaction of soft collagen tissue with minimal dissociation of collagen tissue.
2. Description of the Related Art
Instability of peripheral joints has long been recognized as a significant cause of disability and functional limitation in patients who are active in their daily activities, work or sports. Diarthrodial joints of musculoskeletal system have varying degrees of intrinsic stability based on joint geometry and ligament and soft tissue investment. Diathrodial joints are comprised of the articulation of the ends of bones and their covering of hyaline cartilage surrounded by a soft tissue joint capsule that maintains the constant contact of the cartilage surfaces. This joint capsule also maintains within the joint the synovial fluid that provides nutrition and lubrication of the joint surfaces. Ligaments are soft tissue condensations in or around the joint capsule that reinforce and hold the joint together while also controlling and restricting various movements of the joints. The ligaments, joint capsule, and connective tissue are largely comprised of collagen.
When a joint becomes unstable, its soft tissue or bony structures allow for excessive motion of the joint surfaces relative to each other and in directions not normally permitted by the ligaments or capsule. When one surface of a joint slides out of position relative to the other surface, but some contact remains, subluxation occurs. When one surface of the joint completely disengages and loses contact with the opposing surface, a dislocation occurs. Typically, the more motion a joint normally demonstrates, the more inherently loose the soft tissue investment is surrounding the joint. This makes some joints more prone to instability than others. The shoulder, (glenohumeral) joint, for example, has the greatest range of motion of all peripheral joints. It has long been recognized as having the highest subluxation and dislocation rate because of its inherent laxity relative to more constrained xe2x80x9cball and socketxe2x80x9d joints such as the hip.
Instability of the shoulder can occur congenitally, developmentally, or traumatically and often becomes recurrent, necessitating surgical repair. In fact subluxations and dislocations are a common occurrence and cause for a large number of orthopedic procedures each year. Symptoms include pain, instability, weakness, and limitation of function. If the instability is severe and recurrent, functional incapacity and arthritis may result. Surgical attempts are directed toward tightening the soft tissue restraints that have become pathologically loose. These procedures are typically performed through open surgical approaches that often require hospitalization and prolonged rehabilitation programs.
More recently, endoscopic (arthroscopic) techniques for achieving these same goals have been explored with variable success. Endoscopic techniques have the advantage of being performed through smaller incisions and therefore are usually less painful, performed on an outpatient basis, are associated with less blood loss and lower risk of infection and have a more cosmetically acceptable scar. Recovery is often faster postoperatively than using open techniques. However, it is often more technically demanding to advance and tighten capsule or ligamentous tissue arthroscopically because of the difficult access to pathologically loose tissue and because it is very hard to determine how much tightening or advancement of the lax tissue is clinically necessary. In addition, fixation of advanced or tightened soft tissue is more difficult arthroscopically than through open surgical methods.
Collagen connective tissue is ubiquitous in the human body and demonstrates several unique characteristics not found in other tissues. It provides the cohesiveness of the musculoskeletal system, the structural integrity of the viscera as well as the elasticity of integument. These are basically five types of collagen molecules with Type I being most common in bone, tendon, skin and other connective tissues, and Type III is common in muscular and elastic tissues.
Intermolecular cross links provide collagen connective tissue with unique physical properties of high tensile strength and substantial elasticity. A previously recognized property of collagen is hydrothermal shrinkage of collagen fibers when elevated in temperature. This unique molecular response to temperature elevation is the result of rupture of the collagen stabilizing cross links and immediate contraction of the collagen fibers to about one-third of their original lineal distention. Additionally, the caliber of the individual fibers increases greatly, over four fold, without changing the structural integrity of the connection tissue.
There has been discussion in the existing literature regarding alteration of collagen connective tissue in different parts of the body. One known technique for effective use of this knowledge of the properties of collagen is through the use of infrared laser energy to effect tissue heating. The use of infrared laser energy as a corneal collagen shrinking tool of the eye has been described and relates to laser keratoplasty, as set forth in U.S. Pat. No. 4,976,709. The importance controlling the localization, timing and intensity of laser energy delivery is recognized as paramount in providing the desired soft tissue shrinkage effects without creating excessive damage to the surrounding non-target tissues.
Radiofrequency (RF) electrical current has been used to reshape the cornea. Such shaping has been reported by Doss in U.S. Pat. Nos. 4,326,529; and 4,381,007. However, Doss was not concerned with dissociating collagen tissue in his reshaping of the cornea.
Shrinkage of collagen tissue is important in many applications. One such application is the shoulder capsule. The capsule of the shoulder consists of a synovial lining and three well defined layers of collagen. The fibers of the inner and outer layers extend in a coronal access from the glenoid to the humerus. The middle layer of the collagen extends in a sagittal direction, crossing the fibers of the other two layers. The relative thickness and degree of intermingling of collagen fibers of the three layers vary with different portions of the capsule. The ligamentous components of the capsule are represented by abrupt thickenings of the inner layer with a significant increase in well organized coarse collagen bundles in the coronal plane.
The capsule functions as a hammock-like sling to support the humeral head. In pathologic states of recurrent traumatic or developmental instability this capsule or pouch becomes attenuated and the capsule capacity increases secondary to capsule redundance. In cases of congenital or developmental multi-directional laxity, an altered ratio of type I to type III collagen fibers may be noted. In these shoulder capsules a higher ratio of more elastic type III collagen has been described.
There is a need for a method and apparatus to effect controlled lineal contraction or shrinkage of collagen fibers to provide a multitude of non-destructive and beneficial structural changes and corrections within the body. More particularly with regard to the shoulder capsule, current surgical techniques involve cutting or advancing the shoulder capsule to eliminate capsular redundance or to otherwise tighten the ligamous complex. Accordingly, there is a need to control shrinkage of the capsule by utilizing the knowledge of the properties of collagen in response to a specific level of thermal application.
It is an object of the present invention to provide a method and apparatus to control the duration and application of thermal energy to a tissue site made that includes collagen soft tissue; a desired level of contraction of collagen fibers is obtained while dissociation and breakdown of the collagen fibers is minimized.
Another object of the present invention is to use RF heating in a fluid environment to control thermal spread to a tissue that includes collagen soft tissue, and a desired contraction of collagen fibers is obtained while minimizing dissociation and breakdown of the collagen fibers.
Yet another object of the present invention is to provide a device directed to collagen connective tissue shrinkage by the use of RF heating to a temperature profile of 43 to 90 degrees centigrade.
Another object of the present invention is to provide a device directed to collagen connective tissue shrinkage by the use of RF heating to a temperature profile of 43 to 75 degrees centrigrade.
Still a further object of the present invention is to provide a device directed to collagen connective tissue shrinkage by the use of the RF heating to a temperature profile of 45 to 60 degrees centigrade.
Another object of the present invention is to provide an apparatus which delivers RF energy through an endoscopically guided handpiece in a fluid environment to obtain maximum contraction of collagen soft tissue while minimizing dissociation and breakdown of the collagen tissue.
Yet another object of the present invention is to provide an apparatus that provides for the maximum amount of collagen contraction without dissociation of the collagen structure.
Another object of the present invention is to provide an apparatus to deliver a controlled amount of RF energy to the collagen soft tissue of a joint in order to contract and restrict the soft tissue elasticity and improve joint stability.
A further object of the present invention to provide an apparatus and method that reduces redundancy of the shoulder capsule and improves stability to the joint.
These and other objects of the invention are obtained with an apparatus for control contraction of tissue that includes collagen fibers. The apparatus includes a handpiece, and an electrode with an electrode proximal end that is associated with the handpiece. A distal end of the electrode has a geometry that delivers a controlled amount of energy to the tissue in order to achieve a desired contraction of the collagen fibers. This is achieved while dissociation and breakdown of the collagen fibers is minimized.
The handpiece, with electrode, is adapted to be introduced through an operating cannula in percutaneous applications. Additionally, it may be desirable to include as part of the apparatus an operating cannula. In this instance, the operating cannula has a proximal end that attaches to the handpiece, and a distal end that is adapted to be introduced into a body structure. The electrode is positioned within the operating cannula, and is extendable beyond the distal end of the cannula when thermal energy is delivered to the tissue.
It is recognized that the delivery of the thermal energy to the tissue should be delivered in such a way that none of the tissue is ablated. Additionally, the delivery is achieved without dissociating or breaking down the collagen structure. This can be accomplished in different ways, but it has been discovered that an electrode with radiused edges at its distal end is suitable to obtain this result. The present invention is applicable to a number of different anatomical sites. Depending on the anatomy, it may be necessary to deflect the distal end of the electrode to reach the desired site. Additionally, one side of the electrode may include an insulating layer so that thermal energy is only delivered to the intended tissue, and not a tissue in an adjacent relationship to the area of treatment.
In certain instances it is desirable to be able to vary the length of the electrode conductive surface which delivers the thermal energy to the tissue. For this purpose, an adjustable insulator, that is capable of movement along the longitudinal axis of the electrode, provides a way of adjusting the length of electrode conductive surface.
Memory metals can be used for the electrode construction. An advantage of memory metals is that with the application of heat to the metal, it can be caused to be deflected. This is particularly useful for deflecting the distal end of the electrode.
The electrode can include a central lumen that receives an electrolytic solution from an electrolytic source. A plurality of apertures are formed in the distal end of the electrode and deliver the flowing electrolytic fluid to the tissue. Instead of an electrolytic solution, an electrolytic gel can also be introduced through the electrode.
In one embodiment of the invention, the electrode is partially surrounded by an insulating housing in order to position the electrode in an adjacent but spaced relationship to the tissue. A portion of the insulating housing rides on the tissue, and creates the equivalent of a partial dam for electrolytic solution introduced through the electrode and towards the tissue. A cuff is disposed about the insulating housing. The cuff and insulating housing together create a return electrolytic solution channel for the removal of solution flowing out of the dam and away from the tissue site.
The handpiece of the invention can be connected, with a cable, to an RF energy source. A closed loop feedback system can be included and coupled to a temperature sensor on the electrode and the RF energy source. Temperature at the electrode can be monitored, and the power of the RF energy source adjusted to control the amount of energy that is delivered to the tissue.
The present invention has wide spread application to many different anatomical locations. It can be utilized for controlled contraction of the collagen soft tissue of a joint capsule, particularly the gleno-humoral joint capsule of the shoulder, to treat herniated discs, the meniscus of the knee, for dermatology, to name just a few.
In one embodiment of the invention, RF heating in a fluid or saline environment is used to control thermal spread to soft collagen tissue. The RF energy can be delivered through an endoscopically guided handpiece under arthroscopic visualization by the surgeon. In the temperature range of 43 to 90 degrees C., maximum collagen contraction is achieved. Additional temperature ranges are 43 to 75 degrees C., and 45 to 60 degrees C. Lower temperatures do not provide maximum thermal induced contracture of the collagen fibrils. Greater temperatures create excessive destruction and disintegration of the collagen fibrillar pattern. Thus, the present invention is a method and apparatus which accurately controls the application of heat within a desired thermal range. This heat is delivered to the collagen soft tissue, thereby contracting and restricting the soft tissue elasticity and improving stability.